It is common to employ vacuum contactors in power distribution systems for controlling current flow within a circuit. Each phase of a multi-phase circuit has one vacuum interrupter for controlling the current in that phase. All of the interrupters in the circuit are generally controlled by a single armature and coil. The interrupter stem or tip pressure is directly related to the force applied to the electrical contacts in the closed position and therefor critical to the operation of the interrupter. It will be understood by those skilled in the art that the terms, "stem pressure", "tip pressure", or "sealed pressure of contacts", as used herein, are synonymous and refer to the pressure between the contacts of a particular set of contacts of a vacuum interrupter when the contacts are in the closed position, and is usually measured in terms of the force in pounds exerted on the movable contact by the stem. If the stem pressure is too low, the contacts will close too fast causing them to bounce and produce an arc. The arc will erode the contact surface and may eventually cause welding of the contacts in the closed position. If the stem pressure is too high, the contacts will close too slowly or have insufficient pressure to maintain a good electrical connection. Slow closing of the contacts will prolong arcing and possibly cause welding of the contacts while a poor electrical connection can cause overheating and possible welding of the contacts. The amount of force applied to each interrupter stem is generally controlled by the tolerance of the parts used in the contactor assembly and the precision of the operator in assembling those parts. If the interrupter stem pressures in a multi-phase assembly are not within the specified tolerance range, a partial disassembly of the device and replacement of parts may be required to bring the stem pressures within tolerance. This is time consuming and greatly increases the manufacturing cost of the contactor assembly.